title: Detailing magnetic field strength dependence and segmental artifact distribution of myocardial effective transverse relaxation rate at 1.5, 3.0, and 7.0 T.
abstract: OBJECTIVE
  Realizing the challenges and opportunities of effective transverse relaxation rate (R2 *) mapping at high and ultrahigh fields, this work examines magnetic field strength (B0 ) dependence and segmental artifact distribution of myocardial R2 * at 1.5, 3.0, and 7.0 T.
  
  
  METHODS
  Healthy subjects were considered. Three short-axis views of the left ventricle were examined. R2 * was calculated for 16 standard myocardial segments. Global and mid-septum R2 * were determined. For each segment, an artifactual factor was estimated as the deviation of segmental from global R2 * value.
  
  
  RESULTS
  The global artifactual factor was significantly enlarged at 7.0 T versus 1.5 T (P = 0.010) but not versus 3.0 T. At 7.0 T, the most severe susceptibility artifacts were detected in the inferior lateral wall. The mid-septum showed minor artifactual factors at 7.0 T, similar to those at 1.5 and 3.0 T. Mean R2 * increased linearly with the field strength, with larger changes for global heart R2 * values.
  
  
  CONCLUSIONS
  At 7.0 T, segmental heart R2 * analysis is challenging due to macroscopic susceptibility artifacts induced by the heart-lung interface and the posterior vein. Myocardial R2 * depends linearly on the magnetic field strength. The increased R2 * sensitivity at 7.0 T might offer means for susceptibility-weighted and oxygenation level-dependent MR imaging of the myocardium.
authors.affiliation: CMR Unit, Fondazione G. Monasterio CNR-Regione Toscana and Institute of Clinical Physiology, Pisa, Italy.
authors.forename: Antonella
authors.initials: A
authors.lastname: Meloni
authors.forename: Fabian
authors.initials: F
authors.lastname: Hezel
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Positano
authors.forename: Petra
authors.initials: P
authors.lastname: Keilberg
authors.forename: Alessia
authors.initials: A
authors.lastname: Pepe
authors.forename: Massimo
authors.initials: M
authors.lastname: Lombardi
authors.forename: Thoralf
authors.initials: T
authors.lastname: Niendorf
mesh_terms: D000328:Adult; D016477:Artifacts; D005260:Female; D064368:Healthy Volunteers; D006321:Heart / Q000033:anatomy & histology*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008280:Magnetics; D008297:Male
keywords: 7.0 T; cardiac R2*; cardiac imaging; high field; magnetic resonance imaging; myocardial tissue characterization; susceptibility artifacts; ultrahigh field MR